if it's going to be a special occassion wearer, 5146 if it's for every day.
The 5205 is more dressy and formal, the 5146 more practical. I personally don't like the "cartoon" power reserve indicator on the 5146 and the fat & fluffy numerals at the quarters, but I like the AC complication and moonphase display.
They are both very nice watches, but I chose the 5036 over the 5146, and added a 5205 to my collection.
MW